Method and device for operating voice-controlled systems in motor vehicles

ABSTRACT

A device for operating voice-controlled systems, such as communication and/or intercommunication systems in motor vehicles, includes a plurality of microphones and at least one loudspeaker. Voice signals received by the microphones are transmitted to the at least one loudspeaker. The voice signals are subjected to a low-value frequency shift before being transmitted to the loudspeaker(s) or to the input of a voice-controlled device to thereby suppress feedback.

FIELD OF THE INVENTION

The present invention relates to a method and a device, for operatingvoice-controlled systems, such as communication and/or one-way/two-wayintercom devices in motor vehicles, where voice signals are picked up bya multiple microphone system and transmitted to at least oneloudspeaker.

BACKGROUND INFORMATION

On the one hand, methods of this type are used in motor vehicles forvoice- controlled intercom operation, but they are also used forsupporting voice-input controlled electronic or electric modules. Inthis case, the fundamental problem is that, depending on the operatingstate, corresponding background noise is present in the motor vehicle.This background noise masks the voice commands. One- and two-wayintercom systems in motor vehicles are advantageous in large vehicles,minibusses, and the like. However, they can also be used in normalpassenger cars. Suppressing background noise or filtering out the voicecommand is still very important in the use of voice-controlled inputunits for electric components in the vehicle.

A voice-recognition device for a motor vehicle is described, for examplein European Patent No. 0 078 014, where sensors signal or feed into theamplifier system of the voice- recognition device, whether or not theengine is running and/or the vehicle is moving. This device guides alevel control, by which it is attempted to isolate the voice commandfrom the background noise.

German Patent No. 37 42 929 describes a system having two microphones,one of the microphones being disposed at the mouth of the operator, andanother in proximity, which is, however, for picking up thestructure-borne noise. Both microphone signals are triggered so, thatstructure-borne noise can be subtracted from the total noise.

German Published Patent Application No. 197 05 471 describes avoice-recognition system using transverse filtering. In this case, afrequency analysis is performed, which is only used for the purpose ofrecognizing speech commands. No ambient-noise compensation is performed.

Filtering is described in International Patent Publication No. WO97/34290, in which periodic interference signals are filtered out byascertaining their periods and canceling them out by interference, usinga generator, so that the voice signal remains.

German Patent No. 41 06 405 describes a method in which noise issubtracted from the voice signal, a plurality of microphones being used.

The use of a multiple microphone array is known from described in GermanPublished Patent Application No. 39 25 589. When using the array in themotor vehicle, one of the microphones is disposed in the enginecompartment and another microphone is disposed in the passengercompartment. Both signals are then subtracted. A disadvantage in thiscase, is that only the engine noise i.e. the actual operational noise ofthe vehicle itself, is subtracted from the total signal in the passengercompartment. Specific ambient noises are not, however, considered. Thelack of feedback suppression presents a special problem. Wherevermicrophones and loudspeakers are arranged in acoustically coupleableproximity, the acoustic signal decoupled at the loudspeaker is fed backinto the microphone. This results in so-called feedback and a subsequentoverload.

German Published Patent Application No. 39 25 589 also describes amethod, in which a composite signal is formed. The composite signalincludes a voice signal and an external noise signal. A detection of theexternal noise is performed separately. The external noise and voicesignals are filtered and subtracted from the composite signal. Theresults is used to control the filter. This method, however, cannoteffectively prevent the occurrence of an echo and/or feedback.

A similar method is known from DE 39 25 589 A1, where a composite signalmade of a voice signal and an external signal is formed. The additionalpicking-up of external noise takes place separately. The external-noiseand voice signals are lead over a filter and are subtracted from thecomposite signal. Then, the result of the comparison controls thefilter. A method of this type cannot effectively prevent the

Therefore, it is an object of the present invention to provide a methodand device for operating voice-controlled systems in motor vehicles sothat instances of feedback and

SUMMARY

Regarding a device of the species, the stated object of the presentinvention is achieved by the characterizing features of claim 5.Advantageous further refinements of the device according to the presentinvention are specified in the remaining claims.

With regard to both the method and the device, the present invention isbased on a communication and/or one-way/two-way intercom device in motorvehicles. A multiple microphone system is provided to pick up both voiceand noise signals. Noise signals are subtracted from the total signal,so that the filtered voice signal remains.

The present invention includes initially shifting the frequency of thespecific microphone signal by a small amount Δ F, and only thentransmitting the microphone signal to the loudspeaker(s) or to the inputof a voice-controlled device. The frequency shift of the presentinvention, which is performed at a defined position and is notarbitrary, supports the filtering on the one hand, and decouplesfeedback, and therefore the echo signal, on the other hand. This resultis achieved by subtracting the composite signal shifted by Δ F ofanother, i.e., a second, microphone from the composite signal of a firstmicrophone, the frequency of which has not yet been shifted, and viceversa.

Since, without the aforesaid frequency shift of the present invention,feedback is nothing more than the, fed-back, amplified voice signal,such feedback cannot be eliminated by conventional systems andprocedures. This is therefore the case, because devices conventionalonly separate the voice signal from the noise signal, and identify thefed-back signal as a voice signal, and not as a noise signal. For thisreason, the aforesaid instances of feedback cannot be controlled by theconventional systems and methods and cannot be controlledsimultaneously.

In contrast, the method and the device of the present invention, thelatter of which relates to the connection of the individual elements toone another, eliminate feedback effects in simple and efficient manner.

Since feedback, always occurs when the microphone and loudspeakerlocations are close together, a generally occurs in motor vehicles, theelimination of this feedback is very important. This is not only validin the case of intercom operation, where electroacoustical feedback isuncomfortable for the passengers, but it also has special significancein the use of voice-controlled input interfaces of electrical orelectronic components on the vehicle. This only applies when the entiresystem in the vehicle includes both microphones and loudspeakers, and inthis case, also when the input to electrical devices isvoice-controlled. Feedback and resulting overloads can causeconsiderable malfunctions and misinterpretations of the voice command,even in the case of intelligent input interfaces. Depending on theapplication, this also constitutes a safety hazard. As an option, noisereduction can also be implemented at the same time, i.e.,simultaneously.

The present invention is represented in the drawing, and subsequentlydescribed in detail.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a schematic view of a device for operatingvoice-controlled systems in motor vehicles according to the presentinvention.

DETAILED DESCRIPTION

In the illustrated exemplary embodiment of the present-invention, thevehicle interior is subdivided into two subspaces, namely front andrear.

A microphone M 1 and a loudspeaker L 2 are located in the front section.Microphone M 1 picks up the voice signal, and possibly picks up noisesignals as well. In this case, the noise signal is made up of thebackground noise in the passenger compartment, which occurs whileoperating the vehicle. This background noise may include engine noises,wind noises, rolling noises, but also acoustical echo signals from theother subspace, and the like. The composite signal (total signal) (totalsignal) detected at M 1, which may include of background speech andbackground noise, is fed to a first summation point S 1. Then, acorrespondingly conditioned signal from an acoustic model AM 1 in frontis also fed to this summation point. In this exemplary embodiment, thesubtraction signal generated in acoustic model AM 1 originates from thesignal, which is obtained in the rear section of the vehicle, and isalready shifted in frequency. Because this signal, which comes from M 2,is frequency-shifted in F 2, and originates from the rear subspace ofthe passenger compartment, is also taken into account in front on asignal basis, by AM 1, the signal, which is generated in the rearsubspace of the vehicle, is acoustically transported up front, into thefront subspace of the passenger compartment, and is also registered by M1, is subtracted again at summation point S 1. Thus, the rear subspaceof the passenger compartment is acoustically separated from the frontsubspace of the passenger compartment by device AM 1. That is, the totaldetectable acoustical signal is initially fed into M 1, and the echofrom the rear subspace of the passenger compartment is initiallysubtracted at summation point S 1. The original signal from the frontsubspace of the passenger compartment, which is obtained from M 1 inthis manner, is then supplied to a frequency-shifting device F 1, andshifted by an amount A F, e.g. 5 Hz. The F 1 output signal obtained inthis manner is then supplied to loudspeaker L 1 of the rearpassenger-compartment subspace and, on the other hand, is simultaneouslyfed into device AM 2 in the same manner. In this case, AM 2 againrepresents the acoustic model for the rear subspace of the passengercompartment. A voice message is transmitted in an analogous manner fromthe rear subspace of the passenger compartment, via M 2, to the frontsubspace of the passenger compartment, via L 2. That is, microphone M 2registers the voice message together with the background noise in therear subspace of the passenger compartment, and transmits them tosummation point S 2, which the total acoustical signal picked up by M 1,i.e., the echo as well as ambient noises, is subtracted. In turn, theecho-free signal from microphone M 2, which is generated in this manner,is then supplied to a frequency-shifting device F 2, as well, whichagain shifts the frequency by an amount Δ F. At the output of thisfrequency-shifting device F 2, the result, i.e., the signal conditionedin this manner, is again supplied to the front subspace of the passengercompartment, namely to loudspeaker L 2 positioned there. The frequencyshift for the transmission from the front to the rear can also bedifferent from the frequency shift from the rear to the front.

All in all, the result is a closed, feedback-free system. The shiftingof the frequency is an important feature here, and the echo from thefront to the rear subspace, and vice versa, is eliminated by theinteraction with the connection via acoustic models AM 1 and AM 2.

However, it is also possible to add a noise-signal subtraction to theecho suppression and feedback elimination. This can also beappropriately taken into consideration in the specific acoustic model AM1 and AM 2. The additional components necessary for this purpose, suchas noise-signal microphones, are not shown here in further detail.

Therefore the total background noise signal, which may include an echoand/or other noises, is subtracted from every from every acousticalinput signal from M 1 and M 2, before it is processed further and fed toloudspeakers L 2 and L 1, respectively. So not only does an acousticdecoupling occur between the front and rear subspaces of the passengercompartment, but also the remaining noise signals are quasi compensatedfor, or subtracted, in the same step.

1. A method for operating a voice-controlled system in a motor vehicle,comprising the steps of: detecting a total signal by a plurality ofmicrophones, the total signal including a voice signal and a backgroundnoise signal; performing a frequency shift by an amount of Δ F on thetotal signal detected by each microphone; subtracting thefrequency-shifted total signal of a first one of the plurality ofmicrophones from the detected total signal of a second one of theplurality of microphones before shifting the frequency of the totalsignal of the second one of the plurality of the microphones and viceversa; and transmitting the frequency-shifted total signal to one of aninput to a voice-controlled device and at least one loudspeaker.
 2. Themethod according to claim 1, wherein the voice-controlled systemincludes at least one of a communication device and a two-way intercomdevice.
 3. The method according to claim 1, further comprising the stepsof: defining an arbitrary acoustic model based on the detected totalsignals; and transmitting a signal corresponding to the acoustic modelto a respective summation point for subtraction from the detect totalsignal before the respective frequency shifting.
 4. The method accordingto claim 3, wherein a passenger compartment of the motor vehicle isdivided into at least two acoustic subspaces, each of the acousticsubspaces including at least one microphone location and at least oneloudspeaker location; and wherein the frequency shift is performedbetween the microphone location of one of the subspaces and theloudspeaker location of another one of the subspaces; and wherein eachacoustic model is defined between the microphone location and theloudspeaker location of the respective acoustic subspace to thereby forma signal-based, closed loop electroacoustical control circuit.
 5. Themethod according to claim 4, wherein each acoustic model is defined inaccordance with voice and noise signals detected in the respectiveacoustic subspace and additional noise signals detected in the entirepassenger compartment so that after the signal corresponding to theacoustic model is subtracted from the total signal substantially onlythe voice signal remains.
 6. A device for operating a voice-controlledsystem in a motor vehicle, the motor vehicle including a passengercompartment divided into at least two subsections, each subsectionincluding at least one microphone and at least one loudspeaker, thedevice comprising: a transmitter for transmitting at least one of voicemessages and voice commands; a frequency-shifting device connectedbetween the microphones of one of the subsections and the loudspeakersof another one of the subsections; and a summation point correspondingto each subsection, the summation point subtractively superimposing aparallelly tapped loudspeaker signal and the microphone signal of therespective subsection.
 7. The device according to claim 6, wherein thevoice-controlled system includes at least one of a communication deviceand a two-way intercom device.
 8. The device according to claim 6,wherein the subsections are open subsections.
 9. The device according toclaim 6, further comprising an acoustic model generator provided betweeneach parallel tapped loudspeaker signal and the respective summationpoint, the acoustic models generated at least one of controlling andpostprocessing the respective loudspeaker signal, a resulting signalfrom each acoustic model generator being transmitted to the respectivesummation point.
 10. The device according to claim 9, wherein theacoustic model generators include sound pattern detectors for separatingengine and driving noises from speech-generated acoustical signals andfor separating speech-generated signals from fed-back echo signals. 11.A method for operating a voice-controlled system in a motor vehicle,comprising the steps of: detecting a total signal by a plurality ofmicrophones, the total signal including a voice signal and a backgroundnoise signal; performing a frequency shift by an amount of Δ F on thetotal signal detected by each microphone; subtracting thefrequency-shifted total signal of a first one of the plurality ofmicrophones from the detected total signal of a second one of theplurality of microphones before shifting the frequency of the totalsignal of the second one of the plurality of the microphones and viceversa; and transmitting the frequency-shifted total signal to one of aninput to a voice-controlled device and at least one loudspeaker, whereinΔ F is 5 Hz.
 12. A method for operating a voice-controlled system in amotor vehicle, comprising the steps of: detecting a total signal by aplurality of microphones, the total signal including a voice signal anda background noise signal; performing a frequency shift by an amount ofΔ F on the total signal detected by each microphone; subtracting thefrequency-shifted total signal of a first one of the plurality ofmicrophones from the detected total signal of a second one of theplurality of microphones before shifting the frequency of the totalsignal of the second one of the plurality of the microphones and viceversa; and transmitting the frequency-shifted total signal to one of aninput to a voice-controlled device and at least one loudspeaker, whereinthe frequency shift performed on the total signal of the firstmicrophone is by a first amount Δ F, and the frequency shift performedon the total signal of the second microphone is by a second amount Δ Fdifferent than the first amount Δ F.
 13. A device for operating avoice-controlled system in a motor vehicle, the motor vehicle includinga passenger compartment divided into at least two subsections, eachsubsection including at least one microphone and at least oneloudspeaker, the device comprising: a transmitter for transmitting atleast one of voice messages and voice commands; a frequency-shiftingdevice connected between the microphones of one of the subsections andthe loudspeakers of another one of the subsections; and a summationpoint corresponding to each subsection, the summation pointsubtractively superimposing a parallelly tapped loudspeaker signal andthe microphone signal of the respective subsection, wherein thefrequency-shifting device is configured to perform a frequency shift byan amount of Δ F on each microphone signal.
 14. The device according toclaim 13, wherein Δ F is 5 Hz.